In document WO 91/15292, it has been proposed to produce an active composite by preparing a support formed by a recompressed expanded graphite block which is subsequently impregnated from the outside, for example by a solution of a salt, the impregnated support being subsequently dried in order to produce the active composite. The active composite thus produced has a thermal conductivity markedly higher than that of expanded graphite in the form of folia, while at the same time maintaining a high porosity for gas flows.
Despite undeniable advantages, the active composite prepared according to the method described in document WO 91/15292 is not entirely satisfactory. The reason for this is, on the one hand, that the implementation of this method is lengthy and is difficult to be adapted to large-scale manufacture and, on the other hand, it is difficult to obtain a homogeneous distribution of the active agent within the support. In addition, the act of impregnating the recompressed expanded graphite block via the outside embrittles the outside wall of the block.